i78 PRACTICAL ORGANIC CHEMISTRY
salt. This is ascertained by filtering small samples and testing
the filtrate with potassium carbonate. The liquid is ag-ain
filtered through cloth or through a porcelain funnel and concen-
trated first over a ring burner, and finally on the water-bath,
until a sample crystallises on cooling. The potassium salt is
drained at the pump and dried on porous plate. Yield, about
CGHG + H2S04 = CGH5S03H + H2O.
2CGH5S03H + CaC03=(CcH3SOs)2Ca + C02 + H2O.
Properties. — Colourless pearly plates, which slowly effloresce
in the air and which melt above 300° with slight decomposition ;
very soluble in water. See Appendix^ p. 292.
Benzenesnlphonic Chloride, C0H3SO2C1
Gerhardt, Chiozza, Annalen, 1853. 87, 299.
1 5 grms. potassium benzene sulphonate.
25 „ phosphorous pentachloride.
The potassium benzenesulphonate is carefully dried on the
water-bath, powdered, and mixed with the phosphorus penta-
chloride in a flask.* A vigorous reaction sets in. When it has
abated, the flask is heated on the water-bath for one hour,*
and the mass occasionally stirred with a glass rod. The pro-
duct is poured into a flask containing 200 c.c. cold water and
allowed to stand an hour. The sulphonic chloride, which
separates as an oil, is then extracted with ether, dehydrated
over calcium chloride, decanted, and the ether removed on the
water-bath. Yield, 10 grams of a light brown oil.
Properties. — Colourless oil when pure ; b. p. 246 — 247° witli
decomposition ; m. p. 14° ; distils undecomposed in vacua.